National Down Syndrome Society NDSS Regal Cinema PSA. Courtesy of National Down Syndrome Society (NDSS). Down syndrome occurs when an individual has three, rather than two, copies of the 21st chromosome. This additional genetic material alters the course of development and causes the characteristics associated with Down syndrome. Down syndrome is the most commonly occurring chromosomal condition. One in every 733 babies is born with Down syndrome. There are more than 400,000 people living with Down syndrome in the United States. Down syndrome occurs in people of all races and economic levels. The incidence of births of children with Down syndrome increases with the age of the mother. But due to higher fertility rates in younger women, 80 percent of children with Down syndrome are born to women under 35 years of age. People with Down syndrome have an increased risk for certain medical conditions such as congenital heart defects, respiratory and hearing problems, Alzheimer's disease, childhood leukemia, and thyroid conditions. Many of these conditions are now treatable, so most people with Down syndrome lead healthy lives. A few of the common physical traits of Down syndrome are low muscle tone, small stature, an upward slant to the eyes, and a single deep crease across the center of the palm. Every person with Down syndrome is a unique individual and may possess these characteristics to different degrees or not at all. Life expectancy for people with Down syndrome has increased dramatically in recent decades - from 25 in 1983 to 60 today. People with Down syndrome attend school, work, participate in decisions that affect them, and contribute to society in many wonderful ways.All people with Down syndrome experience cognitive delays, but the effect is usually mild to moderate and is not indicative of the many strengths and talents that each individual possesses. Quality educational programs, a stimulating home environment, good health care, and positive support from family, friends and the community enable people with Down syndrome to develop their full potential and lead fulfilling lives. Researchers are making great strides in identifying the genes on Chromosome 21 that cause the characteristics of Down syndrome. Many feel strongly that it will be possible to improve, correct or prevent many of the problems associated with Down syndrome in the future. Individuals with Down syndrome are becoming increasingly integrated into society and community organizations, such as school, health care systems, work forces, and social and recreational activities. Individuals with Down syndrome possess varying degrees of intellectual disabilities, from very mild to severe. Most people with Down syndrome have IQs in the mild to moderate range of intellectual disability. Due to advances in medical technology, individuals with Down syndrome are living longer than ever before. In 1910, children with Down syndrome were expected to survive to age nine. With the discovery of antibiotics, the average survival age increased to 19 or 20. Now, with recent advancements in clinical treatment, most particularly corrective heart surgeries, as many as 80 percent of adults with Down syndrome reach age 60, and many live even longer. In the United States, approximately 400,000 families have a child with Down syndrome, and about 5,000 babies with Down syndrome are born each year. More and more Americans will interact with individuals with this genetic condition, increasing the need for widespread public education and acceptance.